Methods and devices for establishing security associations and performing handoff authentication in communications systems

ABSTRACT

A method of providing secure communications between a base station, a relay station, and a mobile station in a communication network includes receiving, by the relay station, an unsolicited security key from the base station; receiving, by the relay station, a signaling message from the mobile station; and authenticating, by the relay station, the mobile station using the security key. A method of providing secure communications between a base station, a relay station, and a mobile station in a communication network includes receiving, by the relay station, a signaling message from the mobile station; transmitting, by the relay station, subsequent to receiving the signaling message, a security key request to the base station; receiving, by the relay station, a security key from the base station in response to the previously sent security key request; and authenticating, by the relay station, the mobile station using the received security key.

PRIORITY

This application claims the benefit of priority of U.S. ProvisionalApplication No. 60/969,773, filed Sep. 4, 2007; U.S. ProvisionalApplication No. 60/981,767, filed Oct. 22, 2007; and U.S. ProvisionalApplication No. 60/985,538, filed Nov. 5, 2007, all of which areincorporated by reference herein in their entirety for any purpose.

TECHNICAL FIELD

The present disclosure relates to the field of communications and, moreparticularly, to systems and methods for establishing securityassociations and performing handoff authentication in a communicationsystem.

BACKGROUND

Conventional wireless network environments connect mobile electronicdevices to a service provider. More specifically, WiMAX (WorldwideInteroperability for Microwave Access) network environments connect aclient device, through intermediate connections, to, for example, theInternet. WiMAX is a wireless networking technology that providescommunication to wireless devices over significant distances.Authentication and reauthentication delays, however, can slowcommunication with the client device and decrease the efficiency of aWiMAX environment.

FIG. 1 is a block diagram of an exemplary prior art wirelesscommunication system for use in an IEEE 802.16d/802.16e WiMAX wirelesscommunication system. Access to Internet 100 is provided to at least oneconnectivity service network (CSN) 102, using at least oneauthentication, authorization, and accounting (AAA) server 104. CSN 102is connected to gateways (GWs) 106 and 108. Gateways 106 and 108 aretypically connected to several base stations (BSs) 110-115, the numberof such BSs depending on network demands in a given area, though agateway may instead be connected to only a single base station. Only twogateways 106 and 108 are shown, but it is possible to have greater orfewer gateways depending on the number of required base stations.

In FIG. 1, six base stations are shown as an exemplary WiMAXenvironment, but greater or fewer base stations may be provideddepending on the number of available gateways and the network demands inthe WiMAX environment. Base stations, such as base station 110 and basestation 114, communicate with one or more client devices. Client devicesinclude mobile stations (MSs), such as mobile stations 120, 122 and 124,to which the base stations provide wireless network service, andsubscriber stations (SSs), such as subscriber stations 126 and 128, towhich base stations provide wired or wireless network service. Thenetwork needs of several client devices may be satisfied by a singlebase station, and a single base station may satisfy the network needs ofboth mobile stations and subscriber stations.

In the conventional WiMAX environment, such as that shown in FIG. 1,each time mobile station 120 is initially served by a gateway, e.g.,gateway 106, via an associated base station, e.g., base station 110, itis necessary to authenticate mobile station 120. Following suchauthentication, so long as mobile station 120 moves in areas that enablecontinued service via the original authenticating gateway, no furthergateway authentication is required. However, if mobile station 120 movesto an area served by a different gateway, e.g., gateway 108, mobilestation 120 is handed over to the different gateway, so that it isnecessary for that different gateway to reauthenticate mobile station120 as part of the handoff processing before service may be provided.After a client device has been authenticated or reauthenticated,security associations, or the sharing of security information betweentwo network entities such as mobile station 120 and base station 110,are established to ensure that communications between the two entitiesare secure.

Authentication protocol standards have been created to standardizeadvance authentication techniques. These standardized protocols mayinclude, for example, IEEE 802.1X authentication, extensibleauthentication protocol (EAP) method for global system for mobilecommunications (GSM) subscriber identity (EAP-SIM) and extensibleauthentication protocol method for universal mobile telecommunicationssystems (UMTS) authentication and key agreement (EAP-AKA) and/or acombination of the extensible authentication protocol (EAP) and theremote authentication dial in user service (RADIUS) protocol. Inaddition, standardized handshake protocols, such as security associationsignaling protocols, e.g., security association and traffic encryptionkey (SA-TEK) 3-way handshakes, and traffic encryption key (TEK) 3-wayhandshakes may be used to establish security associations over acommunication link.

In IEEE 802.16d/802.16e WiMAX wireless communication systems, thesestandardized techniques are performed between a base station and amobile station. Each standardized authentication technique requiresmultiple transmissions, which consume authentication time and processingoverhead.

FIG. 2 is a signaling diagram of exemplary prior art authentication andauthorization in an IEEE 802.16d and 802.16e WiMAX wirelesscommunication system. An initialization process 200 is used to ensurethat a mobile station requesting network service is authorized to accessthe network and to provide a security association between mobilestations and base stations to allow secure message transmission. Forexample, initialization process 200 may be used to provide a securityassociation between mobile station 120 just after it moved into therange of base station 111 after previously being within the range ofbase station 110.

In the first step of initialization process 200, mobile station 120 iswirelessly connected to base station 111 through the link up processwhich includes, for example, a signaling message such as ranging request202 and a signaling message such as a ranging response 204. Mobilestation 120 must then go through a multi-step process of authenticationsuch as IEEE 802.1X full authentication 206 with AAA server 104 throughgateway 106. Then AAA server 104 computes a master session key (MSK)(not shown) for mobile station 120 and transfers the MSK to gateway 106,which stores the MSK in its cache. The product of authenticationthrough, for example, the EAP method or other authentication method isthe transfer of the MSK, which is known to AAA server 104, gateway 106,and mobile station 120. Gateway 106 will generate a pairwise master key(PMK) 210 and an authentication key (AK) 212 for mobile station 120, andtransfer AK 212 to base station 111.

Mobile station 120 may also independently hold and store the MSK in itsmemory and may generate AK 212. Then base station 111 may perform SA-TEK3-way handshake procedure 214 to confirm that the AK held by mobilestation 120 is the same AK 212 held by base station 111. Using AK 212,commonly held by base station 111 and mobile station 120, base station111 and mobile station 120 may both calculate respectively averification key, such as a common message authentication code key(MACK) 215 that identifies mobile station 120 and a common keyencryption key (KEK) 218. MACK 215 may identify an authenticated messagegenerated by mobile station 120 and base station 111. KEK 218 mayprotect traffic key delivery from base station 120 to mobile station111. Base station 110 and mobile station 120 may perform SA-TEK 3 wayhandshake procedure 214 with MACK 215 to authenticate each other. WhenSA-TEK 3-way handshake procedure 214 has been successfully completed,base station 110 may generate a traffic key, such as traffic encryptionkey (TEK) 220 and then carry out a TEK 3-way handshake procedure 216with KEK 218 to establish a security association with mobile station120. TEK 220 is typically randomly generated by the base station 111 andis used to encrypt data transmitted between mobile station 120 and basestation 111 after mobile station 120 has been authenticated andauthorized to access the network. SA-TEK 3-way handshake 214 and TEK3-way handshake 216 are well-known in the art and will not be discussedfurther.

In initialization process 200 for use in IEEE 802.16d and 802.16e WiMAXwireless communication systems as shown in FIG. 2, base station 111controls whether data transmission occurs over the channel between basestation 111 and mobile station 120 because base station 111 and mobilestation 120 both hold the same TEK 220, KEK 218, MACK 215, and AK 212.After a mobile station has established a security association with abase station, or, in other words, after a mobile station has beengranted permission to communicate over the network, encrypted datatransmission occurs between the mobile station and the base stationusing the TEK.

Referring again to FIG. 1, in operation, the strength of the signal andtransmission quality may decrease as the network signal travels fromgateway 106 or gateway 108 to base stations 110-115 to client devices120, 122, 124, 126, and 128. Additionally, the signal and transmissionquality decrease as a mobile station travels further from its servingbase station. Signal quality and coverage may also be affected byfactors such as physical structures, signal interferences, weather andtransmission conditions and formats. Therefore, coverage gaps or holesmay exist and users in those areas may have limited or no networkaccess.

One solution to avoid or reduce coverage gaps is to provide more basestations, but this solution can be costly. Alternatively, a network mayavoid or reduce coverage gaps and/or extend its network coverage byusing relay stations (RSs), such as those implementing the concept ofmulti-hop relaying (MR) as set forth in IEEE 802.16j. Typically, basestations communicate with these relay stations, which boost and relaysignals to and from mobile stations and base stations, but otherwise arenot involved in authentication and/or establishing securityassociations.

FIG. 3 is a block diagram of an exemplary prior art wirelesscommunication system for use in an IEEE 802.16j WiMAX wirelesscommunication system with MR architecture. Similar to the IEEE 802.16dand 802.16e WiMAX wireless communication systems, access to Internet 100is provided through at least one AAA server, such as AAA server 104, andvia at least one gateway, such as gateway 106. For convenience, Internet100, CSN 102, AAA server 104 and gateway 106 are referred to as corenetwork 300. Network 300, and specifically, gateway 106, typicallycommunicates with base stations 310-313 over a wired connection.

Four base stations 310-313 are shown in FIG. 3, but greater or fewerbase stations may be provided. Base stations, such as base station 310,may communicate directly with one or more mobile stations, such asmobile station 320, via wireless transmission. Base stations, such asbase station 311 and base station 312, may communicate indirectly withone or more mobile stations, such as mobile stations 322, 324, and 326.Base stations typically communicate with one or more relay stations,such as relay stations 328, 330, and 332, via wireless transmission, butthey may also communicate over wired connections. Relay stations 328,330, and 332 boost and relay the signal to/from mobile station 322 viawireless transmission. As shown, relay stations 328, 330, and 332 arefixed relay stations. However, base stations may also communicate withmobile relay stations (MRSs), such as mobile relay station 334. A mobilerelay station could reside, for example, on a train, plane or automobileand provide its passengers having mobile stations with mobile networkaccess to various base stations and/or relay stations as the mobilerelay station travels. As shown in FIG. 3, mobile relay station 334provides wireless service to mobile stations 324 and 326, but thenetwork needs of only one mobile station, or several mobile stations,may be satisfied by a single mobile relay station. Although not shown,base stations, such as base stations 310-313, may also communicate withone or more subscriber station. The network needs of several clientdevices may be satisfied by a single base station either directly orthrough one or more relay stations. Moreover, relay stations 328, 330,and 332 may provide wireless service to additional relay stations,additional mobile relay stations, and/or additional mobile stations.

In some applications, the use of relay stations may increase the needfor station-to-station (base/relay) handoffs and may require increasedprocessing overhead for such handoffs due to the limited coverage areasof each relay station (including mobile relay stations). In addition,when secure communications are involved, the handoff process from onebase/relay station to another base/relay station may require additionaloverhead and reduce efficiency, bandwidth, or quality of thecommunication connection.

The disclosed embodiments are directed to overcoming one or more of theproblems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to a method ofproviding secure communications between a base station, a relay station,and a mobile station in a communication network. The method receives, bythe relay station, an unsolicited security key from the base station,and receives, by the relay station, a signaling message from the mobilestation. The method also authenticates, by the relay station, the mobilestation using the security key.

In another aspect, the present disclosure is directed to a method ofproviding secure communications between a base station, a relay station,and a mobile station in a communication network. The method receives, bythe relay station, a signaling message from the mobile station, andtransmits, by the relay station, subsequent to receiving the signalingmessage, a security key request to the base station. The method alsoreceives, by the relay station, a security key from the base station inresponse to the previously sent security key request, and authenticates,by the relay station, the mobile station using the received securitykey.

In another aspect, the present disclosure is directed to a method ofproviding secure communications between a target base station, a mobilerelay station, and at least one mobile station in a communicationnetwork. The method transmits, by the mobile relay station, a signalingmessage to the target base station, the signaling message including amessage authentication code (MAC) corresponding to the at least onemobile station. The method also receives, by the mobile relay station, aresponsive signaling message from the target base station and receives,by the mobile relay station, at least one security key corresponding tothe at least one mobile station from the target base station. Inaddition, the method authenticates, by the mobile relay station, the atleast one mobile station using the corresponding security key.

In yet another aspect, the present disclosure is directed to a relaystation for providing secure communications in a communication network.The relay station includes at least one memory to store data andinstructions and at least one processor configured to access the memory.The at least one processor is configured to, when executing theinstructions, authenticate, in response to a signaling message receivedfrom a mobile station, the mobile station using an unsolicited securitykey received from a base station.

In another aspect, the present disclosure is directed to a relay stationfor providing secure communications in a communication network. Therelay station includes at least one memory to store data andinstructions, and at least one processor configured to access thememory. The at least one processor is configured to and configured to,when executing the instructions, subsequent to receiving a signalingmessage from a mobile station, transmit a security key request to a basestation, and authenticate the mobile station using a security keyreceived from the base station in response to the previously transmittedsecurity key request.

In yet another aspect, the present disclosure is directed to a basestation for providing secure communications in a communication network.The base station includes at least one memory to store data andinstructions and at least one processor configured to access the memory.The at least one processor is configured to, when executing theinstructions, cause transmission of, in response to an indication that amobile station entered into a coverage area of a base station, anunsolicited authentication key (AK) received from an authentication,authorization, and accounting server to a relay station.

In another aspect, the present disclosure is directed to a base stationfor providing secure communications in a communication network. The basestation includes at least one memory to store data and instructions, andat least one processor configured to access the memory. The at least oneprocessor is configured to, when executing the instructions, causetransmission of a security key to a relay station in response to asecurity key request received from a relay station.

In yet another aspect, the present disclosure is directed to a systemfor providing secure communications. The system includes a base stationconfigured to provide access to a communication network, authenticate amobile station over the network, receive at least one security key, andpre-distribute the at least one security key. The system also includes arelay station in communication with the base station for receiving thepre-distributed at least one security key unsolicited, and for providingsecure data transmissions to the authenticated mobile station using thesecurity key. The security key includes at least one of anauthentication key (AK) and a verification key.

In another aspect, the present disclosure is directed to a system forproviding secure communications. The system includes a base stationconfigured to provide access to a communication network, authenticate amobile station over the network, receive at least one security key,receive at least one security key request, and transmit the at least onesecurity key in response to the security key request. The system alsoincludes a relay station in communication with the base station fortransmitting the at least one security key request to the base station,for receiving the at least one security key from the base station inresponse to the security key request, and for providing secure datatransmissions to a mobile station using the security key. The securitykey includes at least one of an authentication key (AK) and averification key.

In another aspect, the present disclosure is directed to a method ofproviding secure communications between a base station, a relay station,and a mobile station in a communication network. The method performs keydistribution upon receipt of a key request from the relay station todistribute a verification key corresponding to the mobile station to therelay station, and performs key verification, by the relay station, toidentify the mobile station.

In another aspect, the present disclosure is directed to a method ofproviding secure communications between a base station, a relay station,and a mobile station in a communication network. The method performs keypre-distribution to distribute an unsolicited verification keycorresponding to the mobile station to the relay station, and performskey verification, by the relay station, to identify the mobile station.

In yet another aspect, the present disclosure is directed to a method ofproviding secure communications between a base station, a relay station,and a mobile station in a communication network. The method performs keyverification, by the relay station, to identify the mobile station, andperforms key verification, by the mobile station, to identify the relaystation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary prior art wirelesscommunication system for use in an IEEE 802.16d/802.16e WiMAX wirelesscommunication system.

FIG. 2 is a signaling diagram of exemplary prior art authentication andauthorization in an IEEE 802.16d and 802.16e WiMAX wirelesscommunication system.

FIG. 3 is a block diagram of an exemplary prior art wirelesscommunication system for use in an IEEE 802.16j wireless communicationsystem with multi-hop relaying architecture.

FIG. 4 is a block diagram of an exemplary wireless communication systemfor use in an IEEE 802.16j wireless communication system in whichselected relay stations serve as authenticator relay-relay stations.

FIG. 5 a is a block diagram illustrating an exemplary construction of abase station.

FIG. 5 b is a block diagram illustrating an exemplary construction of amobile station.

FIG. 5 c is a block diagram illustrating an exemplary construction of arelay station or mobile relay station.

FIG. 6 is a signaling diagram of exemplary authentication andauthorization in an IEEE 802.16j wireless communication system in whichselected relay stations serve as authenticator relay-relay stations.

FIG. 7 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station does notcurrently hold a required authentication key.

FIG. 8 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station receives anauthentication key through unsolicited key pre-distribution.

FIG. 9 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station receives anauthentication key through on-demand key distribution.

FIG. 10 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station currently hasan authentication key corresponding to the mobile station being handedoff.

FIG. 11 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station currently hasan authentication key AK corresponding to the mobile station beinghanded off.

FIG. 12 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station currently hasan authentication key that does not correspond to the mobile stationbeing handed off.

FIG. 13 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to the same basestation where the target authenticator relay-relay station currently hasan authentication key that does not correspond to the mobile stationbeing handed off.

FIG. 14 is a signaling diagram of an exemplary mobile station handoffbetween a current authenticator relay-relay station and a targetauthenticator relay-relay station that are connected to different basestations.

FIG. 15 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station.

FIG. 16 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station wherethe target base station communicates with a different gateway and wherea mobile relay station can receive authentication keys and serve as anauthenticator for mobile stations.

FIG. 17 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station, inwhich the base stations are connected to the same gateway.

FIG. 18 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station, inwhich the base stations are connected to the same gateway.

DETAILED DESCRIPTION

Embodiments of the disclosure can provide such security associations inIEEE 802.16j WiMAX wireless communication systems or other wirelesscommunication networking systems that employ relay stations. Byproviding a relay station (RS) with the ability to establish a secureconnection with mobile stations and provide mobile stations with accessto the network, processing overhead can be significantly reduced.Specifically, by providing a relay station with the security materialcorresponding to a mobile station seeking access to the network, therelay station can establish a security association quickly with themobile station and perform mobile station authentication andauthorization when mobile station handoff occurs.

FIG. 4 is a block diagram of an exemplary wireless communication systemfor use in an IEEE 802.16j WiMAX wireless communication system in whichselected relay stations serve as authenticator relay-relay stations(AR-RSs). In FIG. 4, a base station 400 is connected over a wire tonetwork 300 and communicates wirelessly with one or more relay stations402 and 404, which boost and relay the received signal to AR-RSs406-409. As shown in FIG. 4, AR-RS 408 is a mobile relay station. Arelay key (RK) 410 is distributed by base station 400 to selected relaystations within the area of coverage for base station 400, for example,relay stations 402 and 404, and AR-RSs 406-409 after relay stations 402and 404, and AR-RSs 406-409 are authenticated during theirinitialization to network 300. Relay key (RK) 410 is used to providedata and signal protection and can be used to protect data and/ormanagement messages for the communication channels between relaystations and/or between relay stations and base stations in an IEEE802.16j network. The area of network coverage provided by base station400, relay stations 402 and 404, and AR-RSs 406-409 that hold a commonparticular type of relay key 410, called a security zone key, may becalled a secure relay zone (SRZ) 412. FIG. 4 illustrates a single mobilestation 414 served by AR-RS 406 and two mobile stations 416 and 418 areserved by AR-RS 408, but the network needs of several mobile stationsmay be provided by a single AR-RS. In addition, although only AR-RS 408is shown as a mobile relay station, additional AR-RSs within SRZ 412 maybe mobile relay stations.

Each time mobile station 414 is initially served by base station 400, itis necessary to establish a security association with network 300. Solong as mobile station 414 moves within SRZ 412, it may be possible tobypass further security association establishment and authentication.However, if mobile station 414 moves to an area served by a differentbase station, mobile station 414 is handed over to the different basestation, so that it may be necessary for that different base station toestablish another security association with mobile station 414, and,depending upon whether the different base station is connected throughgateway 106, authenticate mobile station 414 as part of the handoffprocessing. Such reauthentication and/or security associationestablishment introduces delay in providing service to mobile station414.

FIG. 5 a is a block diagram illustrating an exemplary construction of abase station such as base station 400. Base station 400 may be any typeof communication device configured to transmit and/or receive dataand/or communications to and from one or more mobile stations such asmobile station 414, relay stations such as relay stations 402 and 404,and/or AR-RSs such as AR-RSs 406-409, in a wireless communicationsystem. As shown in FIG. 5 a, each base station 400 may include one ormore of the following components: at least one central processing unit(CPU) 500 configured to execute computer program instructions to performvarious processes and methods, random access memory (RAM) 502 and readonly memory (ROM) 504 configured to access and store information andcomputer program instructions, memory 506 to store data and information,database 508 to store tables, lists, or other data structures, I/Odevices 510, interfaces 512, antennas 514, etc. Each of these componentsis well-known in the art and will not be discussed further.

FIG. 5 b is a block diagram illustrating an exemplary construction of amobile station such as mobile station 414. As shown in FIG. 5 b, eachmobile station 414 may include one or more of the following components:at least one CPU 520 configured to execute computer program instructionsto perform various processes and methods, RAM 522 and ROM 524 configuredto access and store information and computer program instructions,memory 526 to store data and information, database 528 to store tables,lists, or other data structures, I/O devices 530, interfaces 532,antennas 534, etc. Each of these components is well-known in the art andwill not be discussed further.

FIG. 5 c is a block diagram illustrating an exemplary construction of arelay station or mobile relay station such as AR-RS/mobile relay station406. As shown in FIG. 5 c, each relay station/mobile relay station 406may include one or more of the following components: at least one CPU540 configured to execute computer program instructions to performvarious processes and methods, random access memory RAM 542 and readonly memory ROM 544 configured to access and store information andcomputer program instructions, memory 546 to store data and information,database 548 to store tables, lists, or other data structures, I/Odevices 550, interfaces 552, antennas 554, etc. Each of these componentsis well-known in the art and will not be discussed further.

I. Initialization

FIG. 6 is a signaling diagram of exemplary authentication andauthorization in an IEEE 802.16j WiMAX wireless communication system inwhich selected relay stations serve as authenticator relay-relaystations. An initialization process 600 is used to ensure that a mobilestation requesting network service is authorized to access network 300and to provide a security association between mobile stations, relaystations and AR-RSs for secure message transmission. For example,process 600 may be used to authenticate and establish a securityassociation with mobile station 414 just after it is turned on, or afterit has moved into the coverage area provided by AR-RS 406 from acoverage area provided through a base station connected to gateway 108.First, in accordance with the IEEE 802.16 protocol, mobile station 414sends a signaling message such as ranging request 602 to AR-RS 406 toindicate that mobile station 414 is within range of AR-RS 406. Next,again in accordance with IEEE 802.16 protocol, AR-RS 406 requestsauthentication from base station 400 through a mobile stationauthentication request 604 and transmits a ranging response 606 tomobile station 414 to confirm the signal range of mobile station 414 andreceipt of the ranging request 602. Because mobile station 414 has notpreviously or recently been connected to network 300 through basestation 400 and gateway 106, mobile station 414 performs IEEE 802.1Xfull authentication 206 with AAA server 104. As a result of IEEE 802.1Xfull authentication protocol 206, gateway 106 will receive an MSK fromAAA server 104 and then derive and store PMK 608 and a master key, suchas AK 610, from the MSK for mobile station 414. A master key, such as AK610, is a key from which other security material and/or security keyscan be derived. Next gateway 106 transfers AK 610 to base station 400securely. After receiving AK 610 from gateway 106, base station 400 maytransfer AK 610 to AR-RS 406 directly for establishing a securityassociation between mobile station 414 and relay station 406. Mobilestation 414 may calculate MSK, PMK 608 and AK 610 by itself.

In one exemplary embodiment, to allow AR-RS 406 to perform futureauthentication protocols and to establish a security association withmobile station 414, base station 400 transmits key response 614, whichincludes AK 610, to AR-RS 406. The AR-RS 406 may derive KEK 218 and averification key such as MACK 618 from the AK 610 first. Then the AR-RS406 may perform SA-TEK 3-way handshake procedure 214 locally, protectedby MACK 618, with the mobile station 414. When the SA-TEK 3-wayhandshake procedure 214 is successfully completed, the AR-RS 406 maygenerate a random number to use as a TEK 616 and securely transfer thetraffic key, such as TEK 616, protected by KEK 218, to mobile station414. Finally, AR-RS 406 and mobile station 414 may utilize TEK 616 toprotect data transmission between them and MACK 618 to authenticate eachother.

FIG. 6 illustrates exemplary authentication and authorization in an IEEE802.16j wireless communication system in which selected relay stationsserve as AR-RSs. One of skill in the art will appreciate that the AR-RSin FIG. 6 could be a mobile relay station such as AR-RS 408. One ofskill in the art will also appreciate that instead of sending AK 610 toAR-RS 406, base station 400 may send different security material tomobile stations such as AR-RS 406. For example, upon receiving AK 610,base station 400 may generate MACK 618 using AK 610 and send MACK 618 torelay station 406 instead of sending AK 610. Relay station 406 may useMACK 618 to authenticate, or verify the identity of mobile stations.Mobile station 414 and AR-RS 406 can check the MAC inside the payload,or data component of a MAC packet to authenticate each other, andthereby identify each other.

II. Intra-Base Station Handoffs

FIG. 7 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS does not currently hold therequired AK. A handoff process 700 is used to ensure that a mobilestation requesting network service from a target AR-RS is authorized toaccess the network and to provide a security association between mobilestations and AR-RSs to allow secure message transmission. For example,handoff process 700 may be used to handoff mobile station 414, which hasbeen previously authenticated using AR-RS 406 through the processdescribed above in FIG. 6, from AR-RS 406 to AR-RS 407, where AR-RS 407does not currently have the AK associated with mobile station 414, i.e.,AK 610, in its memory (e.g., memory 546, ROM 544, RAM 542 or database548), but both AR-RS 406 and AR-RS 407 are connected to network 300through base station 400.

In handoff process 700, mobile station 414 first sends a signalingmessage such as a ranging request 602 to AR-RS 407 to indicate thatmobile station 414 is within the coverage area of AR-RS 407. Rangingrequest 602 may include security material identification such as amobile station message authentication code, HMAC and/or CMAC, whichidentifies mobile station 414 as the requesting mobile station.Alternatively, ranging request 602 may include, for example, an AKID.Each of AKID, MS MAC, HMAC, and/or CMAC provide AR-RS 407 withidentification information for mobile station 414 and can be used torequest AK 610 from base station 400 if AR-RS 407 does not hold AK 610.For example, if an AKID is included, AR-RS 407 may decide toauthenticate the corresponding mobile station if AR-RS 407 holds theactive AK, or, if AR-RS 407 does not hold the active AK, can request theactive AK from base station 400. If an AKID is not included in rangingrequest 602, other security material identification can be used toverify the AK held by mobile station 414. Because AR-RS 407 does notcurrently have AK 610 in its memory (e.g., memory 546, ROM 544, RAM 542or database 548), AR-RS 407 transmits a key request 704 to base station400. Key request 704 includes a MAC/HMAC/CMAC corresponding to mobilestation 414. AR-RS 407 transmits a ranging response 606 to mobilestation 414 to confirm the presence of mobile station 414 and receipt ofranging request 602.

Upon receiving key request 704, base station 400 verifies thecredentials of mobile station 414. Base station 400 may retrieve AK 610from its memory (e.g., memory 506, ROM 504, RAM 502 or database 508),and because mobile station 414 has previously undergone IEEE 802.1X fullauthentication 206 with mobile station 414 to obtain AK 610 when mobilestation 414 was connected to AR-RS 406, it is not necessary for basestation 400 and mobile station 414 to again undergo this process. Assuch, base station 400 transmits a key response 612 that includes AK 610to AR-RS 407, thereby granting AR-RS 406 the authority to furtherauthenticate and securely communicate with mobile station 414.

Upon receipt of the ranging response 606, the mobile station 414 mayattempt to initiate authentication using extended authenticationprotocol (EAP) to begin IEEE 802.1X full authentication 206. If AR-RS407 receives such a request, for example a privacy key managementextended authentication protocol (PKM-EAP), which supports IEEE 802.16d,or a PKMv2-EAP, which supports IEEE 802.16e, start request 708, AR-RS407 may transmit a PKMv2-EAP complete message 710 to mobile station 414that indicates to mobile station 414 that IEEE 802.1X fullauthentication 206 is successful without actually undergoing IEEE 802.1Xfull authentication 206.

After AR-RS 407 has AK 610, it may perform SA-TEK 3-way handshake 214and/or TEK 3-way handshake 216 with mobile station 414 to establish asecure connection with mobile station 414. During TEK 3-way handshake216, AR-RS 407 may transmit to the mobile station 414 a new traffic keysuch as TEK 712, generated by AR-RS 407 and encrypted using KEK 218.AR-RS 407 and mobile station 414 may then communicate over a securecommunication channel.

FIG. 8 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS receives the AK throughunsolicited key pre-distribution. As shown in FIG. 8, base station 400receives an indication that mobile station 414 is about to enter or hasrecently entered the coverage area of AR-RS 407. Base station 400 mayreceive this indication from another base station or from gateway 106through BS-BS or BS-gateway communication using additional signalingmessages or a prediction technique such as a global position system(GPS). Because mobile station 414 has previously undergone IEEE 802.1Xfull authentication 206 to obtain AK 610 when mobile station 414 wasconnected to AR-RS 406, it is not necessary for base station 400 andmobile station 414 to again undergo this process. As such, base station400 transmits an unsolicited key pre-distribution signal 802 thatincludes AK 610 and, optionally, TEK 616, to AR-RS 407, thereby grantingAR-RS 407 the authority to authenticate and provide secure communicationwith mobile station 414. This may occur before or in place of mobilestation 414 sending a signaling message and AR-RS 407 transmitting a keyrequest. Then, when mobile station 414 sends ranging request 602, AR-RS407 already holds AK 610 and may simply perform a MAC check 804 toverify the key held by mobile station 414 and thereby verify theidentity of mobile station 414. AR-RS 407 may then send ranging response806 that includes HMAC or CMAC.

In an exemplary embodiment as shown in FIG. 8, a handoff between acurrent AR-RS and a target AR-RS has improved efficiency through theelimination of not only IEEE 802.1X full authentication but also SA-TEK3-way handshake 214 and TEK 3-way handshake 216. SA-TEK 3-way handshake214 and TEK 3-way handshake 216 can be eliminated for previouslyauthenticated mobile stations by providing an AR-RS with the TEK forthese previously authenticated mobile stations. Specifically, in oneembodiment, a target AR-RS may receive a TEK from the current AR-RS thathas previously created a TEK for transmission with mobile station 414;in another embodiment a target AR-RS may receive a TEK from the basestation, which has either previously created the base station throughdirect transmission with the mobile station or which has received a TEKfrom a previous AR-RS. Thus, as shown in FIG. 8, base station 400 cansend TEK 616 to AR-RS 407 either as part of unsolicited keypre-distribution 802 or through a separate transmission. Alternatively,AR-RS 407 may receive TEK 616 from AR-RS 407. If AR-RS 407 holds TEK616, it can skip SA-TEK 3-way handshake 214 and TEK 3-way handshake 216to thereby improve the efficiency the handoff from AR-RS 407. Once AR-RS407 obtains a TEK, either from AR-RS 407, base station 400, or bygenerating a new TEK itself through SA-TEK 3-way handshake 214 and TEK3-way handshake 216, AR-RS may then provide secure communications withmobile station 414, where the data is encrypted using the TEK.

FIG. 9 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS receives the AK throughon-demand key distribution. As shown in FIG. 9, mobile station 414transmits a signaling message such as ranging request 602 to AR-RS 407and upon receiving key request 704, base station 400 verifies thecredentials of mobile station 414. Because mobile station 414 haspreviously undergone IEEE 802.1X full authentication 206 to obtain AK610, it is not necessary for base station 400 and mobile station 414 toagain undergo this process. As such, base station 400 transmits a keyresponse 612 that includes AK 610 and, optionally, TEK 616, to AR-RS407, thereby granting AR-RS 407 the authority to authenticate andprovide secure communication with mobile station 414. Then, AR-RS 407may simply perform a MAC check 804 to verify the key held by mobilestation 414 and thereby verify the identity of mobile station 414. AR-RS407 may then send ranging response 806 that includes HMAC or CMAC tomobile station 414.

As discussed above in connection with FIG. 8, if AR-RS 407 received TEK616 from base station 400, or alternately, received TEK 616 from AR-RS406, AR-RS 407 can skip SA-TEK 3-way handshake 214 and TEK 3-wayhandshake 216 to thereby improve the efficiency of the handoff fromAR-RS 407.

FIG. 10 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS currently has the AKcorresponding to the mobile station being handed off. For example, ifmobile station 414 authenticates with AR-RS 406 as described for FIG. 6,leaves the coverage area of AR-RS 406 and enters the coverage area ofAR-RS 407, and then returns to the coverage area of AR-RS 406, AR-RS 406may still hold AK 610 in its memory (e.g., memory 546, ROM 544, RAM 542or database 548). Thus, when mobile station 414 sends a signalingmessage such as a ranging request 1002 that includes an authenticationkey identification (AKID) corresponding to AK 610, AR-RS 406 sends anAKID Verify request 1004 to base station 400 to confirm the location ofmobile station 414.

Upon receiving the AKID Verify request 1004, base station 400 verifiesthe location of mobile station 414. Because mobile station 414 haspreviously undergone IEEE 802.1X full authentication 206 to obtain AK610, it is not necessary for base station 400 and mobile station 414 toagain undergo this process. As such, base station 400 transmits a keyresponse 1006 that includes AK 610 to AR-RS 407 if AR-RS 406 holds AK610, thereby granting AR-RS 407 the authority to authenticate andestablish a security association with mobile station 414. If AR-RS 406does not hold AK 610 or if it AR-RS 406 needs to confirm that it holdsthe proper AK 610, AR-RS 406 can send RNG Response 606 after receivingkey response 1006 from base station 400.

Upon receipt of the ranging response 1008, the mobile station 414 mayattempt to initiate extended authorization protocol to begin IEEE 802.1Xfull authentication as described above in connection with FIG. 7. Asdescribed above, because AR-RS 407 already has AK 610, AR-RS 407 maytransmit an extended authorization protocol complete message to mobilestation 414 without actually undergoing the processing for IEEE 802.1Xauthentication.

When AR-RS 407 has AK 610, it may perform one or both of SA-TEK 3-wayhandshake 214 and TEK 3-way handshake 216 with mobile station 414 toprepare for data transmission. As shown in FIG. 10, AR-RS 407 may createa new TEK 1010 to encrypt the data transmitted between the AR-RS 407 andthe mobile station 120 after the mobile station 120 has beenauthenticated. As described above, if AR-RS 406 already has TEK 616,AR-RS 406 can skip SA-TEK 3-way handshake 214 and TEK 3-way handshake216 to thereby improve the efficiency of the handoff from AR-RS 407 andestablish a secure association between AR-RS 406 and mobile station 414.

FIG. 11 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS currently has the AKcorresponding to the mobile station being handed off. In such animproved-efficiency handoff, when mobile station 414 sends rangingrequest 602, AR-RS 406 already holds AK 610 and may simply perform a MACcheck 804 to verify the key held by mobile station 414 and therebyverify the identity of mobile station 414. AR-RS 406 may then sendranging response 806 that includes HMAC or CMAC.

FIG. 12 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS currently has an AK that doesnot correspond to the mobile station being handed off. For example,mobile station 414 may enter the coverage area of AR-RS 408 when AR-RS408 holds an AK 1202, which corresponds to a mobile station other thanmobile station 414, but not AK 610, corresponding to mobile station 414,stored in its memory (e.g., memory 546, ROM 544, RAM 542 or database548). Thus, when AR-RS 407 sends an AKID Verify request 1004 to basestation 400 to confirm the location of mobile station 414, base station400 responds with the correct AK corresponding to mobile station 414,i.e., AK 610.

Upon receipt of ranging response 1008, mobile station 414 may attempt toinitiate extended authorization protocol to begin IEEE 802.1X fullauthentication as described above in connection with FIG. 7. Asdescribed above, because AR-RS 408 now has AK 610, AR-RS 408 maytransmit an extended authorization protocol complete message to mobilestation 414 without actually undergoing the processing for IEEE 802.1Xauthentication.

When AR-RS 408 has AK 610, it may perform one or both of SA-TEK 3-wayhandshake 214 and TEK 3-way handshake 216 with mobile station 414 toprepare for data transmission. As shown in FIG. 10, AR-RS 408 may createa new traffic key such as TEK 1204 to encrypt the data transmittedbetween the AR-RS 408 and the mobile station 120 after the mobilestation 120 has been authenticated.

FIG. 13 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected to thesame base station where the target AR-RS currently has an AK that doesnot correspond to the mobile station being handed off. When mobilestation 414 sends a signaling message such as ranging request 602, AR-RS408 holds AK 1202 and when AR-RS 408 performs a MAC check 804 to verifythe key held by mobile station 414 and thereby verify the identity ofmobile station 414, the MAC check is unsuccessful. When AR-RS 408 sendsAKID Verify request 1004 to base station 400 to confirm the location ofmobile station 414, base station 400 responds with the proper AK, i.e.,AK 610. AR-RS 408 may then send ranging response 806 that includes HMACor CMAC. If AR-RS 408 already has TEK 616, AR-RS 408 can skip SA-TEK3-way handshake 214 and TEK 3-way handshake 216.

FIGS. 7-13 illustrate exemplary mobile station handoffs between acurrent AR-RS and a target AR-RS that are connected to the same basestation. Although the scenarios described above in connection with FIGS.12 and 13 are described in the context of a mobile station, i.e., AR-RS408, one of skill in the art will appreciate that the current AR-RS orthe target AR-RS in FIGS. 12 and 13 could be a fixed relay station. Oneof skill in the art will also appreciate that the current AR-RS or thetarget AR-RS in each of the scenarios illustrated above in connectionwith FIGS. 7-11 could be a mobile relay station such as AR-RS 408.

One of skill in the art will also appreciate that, in each of thescenarios illustrated above in connection with FIGS. 7-13, instead ofsending AK 610 to AR-RS 406-409, base station 400 may send differentsecurity material to relay stations. For example, base station 400 maygenerate a verification key, such as MACK 618, and a traffic key, suchas TEK 616, using AK 610, and pre-distribute the verification key andtraffic key to relay station 407 instead of sending AK 610.

Similarly, upon receipt of key request 704, base station 400 maygenerate a verification key, such as MACK 618 using AK 610 and send theMACK to AR-RS 407 at key response 612 for use in MAC Check 804. Inaddition, if AR-RS 406 already has MACK 618 corresponding to mobilestation 414 in its memory (e.g., memory 546, ROM 544, RAM 542 ordatabase 548), upon receiving a signaling message such as a rangingrequest 602, AR-RS 406 may perform a MAC check 804; if relay station 406has the wrong MACK 1206 in its memory, upon receiving a signalingmessage such as a ranging request 602 AR-RS 408 can transmit an AKIDverify signal 1004 and receive MACK 618 in key transfer 1008 from basestation 400.

AR-RSs 405-409 may use MACK 618 to authenticate, or verify the identityof mobile stations as part of MAC Check 804. Mobile station 414 andAR-RSs 405-409 may check the MAC inside the payload, or data componentof a MAC packet, to authenticate each other, or in other words, toidentify each other.

III. Inter-Base Station Handoffs

FIG. 14 is a signaling diagram of an exemplary mobile station handoffbetween a current AR-RS and a target AR-RS that are connected todifferent base stations. An initialization process 1400 is used toensure that a mobile station requesting network service is authorized toaccess network 300 and to provide a security association between mobilestations and AR-RSs to allow secure message transmission. For example,process 1400 may be used to authenticate and authorize mobile station414 just after it moved from AR-RS 408 into the coverage area providedby a target base station 1402 as relayed by a target AR-RS 1404. AK 610is currently stored in mobile station 414, whereas target base station1402 and target AR-RS 1404 have AK 1406 stored in their respectivememories. As shown in FIG. 14, target base station 1402 is connected tothe same gateway as AR-RS 408, from which mobile station 414 is beinghanded off, however, the initialization process 1400 will not change iftarget base station 1402 is connected to a different gateway than AR-RS408.

Mobile station 414 sends a signaling message such as ranging request1002, which includes authentication key identification, to target AR-RS1404 to indicate that mobile station 414 is within range of target AR-RS1404. Target AR-RS 1404 transmits a mobile station authenticationrequest 1407, which includes authentication key identification, totarget base station 1402. Target base station 1402 receives the mobilestation authentication request 1407 but it cannot verify mobile station414 because target base station 1402 does not recognize AK 610.Therefore, target base station 1402 may transmit an authenticationfailure response 1408 to target AR-RS 1404, which may transmit a rangingresponse 1409 to mobile station 414. Target base station 1402 may thenrequire mobile station 414 to authenticate with AAA server 104 usingIEEE 802.1X full authentication protocol 206. As a result of IEEE 802.1Xfull authentication protocol 206, gateway 106 distributes to mobilestation 120 a PMK 1410. Gateway 106 also transmits an AK 1412 to targetbase station 1402 via AK Transfer 612. Mobile station 414 calculates AK610 independently from PMK 1410.

In one exemplary embodiment, to allow target AR-RS 1404 to performadditional authentication steps to provide additional security to thenetwork connection with mobile station 414, base station 400 transmitskey response 614, which includes AK 1412, to target AR-RS 1404. Whentarget AR-RS 1404 has AK 1412, it may perform one or both of SA-TEK3-way handshake 214 and TEK 3-way handshake 216 with mobile station 414to provide further security to the network connection with mobilestation 414. During TEK 3-way handshake 216, AR-RS 1404 transmits to themobile station 414 a traffic key such as TEK 1414, encrypted using KEK1416. TEK 1414 may be randomly generated by the target AR-RS 1404.

FIG. 14 illustrates exemplary mobile station handoffs between a currentAR-RS and a target AR-RS that are connected to different base stations.One of skill in the art will appreciate that the current AR-RS or thetarget AR-RS may be a mobile relay station such as AR-RS 408.

One of skill in the art will also appreciate that, in the scenarioillustrated above in connection with FIG. 14, instead of sending AK 610to AR-RS 406-409, base station 400 may send different security materialto relay stations 406-409. For example, upon receiving AK 1412, basestation 1402 may generate a verification key, e.g., MACK 618, using AK610 and may send the verification key to AR-RS 1404 instead of sendingAK 1412.

IV. Mobile Relay Station Handoffs

Although the processes described above for initialization and handoffsapply to mobile relay stations as well, mobile relay stations and themobile stations accessing the network from within mobile relay stationsmust also be prepared for a change in base station where the AR-RS(specifically, the mobile relay station) does not change.

FIG. 15 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station. InFIG. 15, mobile relay station AR-RS 408 may associate with a target basestation 1502 when AR-RS 408 has moved or is about to move into thecoverage area for target base station 1502. Mobile stations 416 and 418are connected to AR-RS 408 and their connection with AR-RS 408 ispreferably maintained throughout the transition to target base station1502. In order to update the AKs of mobile stations 416 and 418, AR-RS408 may issue a ranging message 1504 to target base station 1502 thatindicates to base station 1502 that AR-RS 408 is within or approachingthe coverage area for target base station 1502. Upon receipt of rangingmessage 1504, AR-RS 408 undergoes one or more of IEEE 802.1Xauthentication 206, SA-TEK 3-way handshake 214, and TEK 3-way handshake216 with gateway 106 and AAA 104. As such, AR-RS 408 must receive an AKand be authenticated in a similar manner to authentication of a mobilestation. Gateway 106 may transfer the AK for the mobile relay station atan AK Transfer 1506.

AR-RS 408 transmits a re-authentication trigger message 1508 to mobilestations 416 and 418. Upon receipt of the re-authentication triggermessage 1508, the mobile stations 416 and 418 perform IEEE 802.1X fullauthentication 206 with gateway 106 and AAA server 104. Gateway 106 maycalculate a new AK obtained from the existing PMK in the gateway fortarget base station 1502. Gateway 106 transfers all of the AKs for themobile stations associated with AR-RS 408 at an AK Transfer 1510, andmay do so in a tunnel mode, in which all of the parameters (e.g., AKs)of all mobile stations connecting to AR-RS 408 are transmitted at onetime. In tunnel mode, the logical connection between two nodes, e.g.,AR-RS 408 and gateway 106 is dedicated, and intermediate nodes (e.g.,target base station 1502) do not process the tunnel packets but ratheronly forward them on. Mobile stations 416 and 418 then undergo SA-TEK3-way handshake 214 with target base station 1502. Target base station1502 will provide traffic keys and AKs for each of the mobile stationsto AR-RS 408 at a TEK Transfer 1512, and may do so using tunnel mode. Inone embodiment, the AKs are received at base station 1502 and mobilestations 416 and 418 prior to the inter-base station handoff to avoid adisconnect in service to mobile stations 416 and 418.

One of skill in the art will appreciate that although FIG. 15 showstarget base station 1502 communicating with the network and AAA server104 via gateway 106, target base station 1502 may also communicate withthe network and AAA server 104 via gateway 108, or another gateway, withthe same processing as described in FIG. 15.

FIG. 16 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station where atarget base station 1600 communicates with a different gateway, i.e., agateway 1602, and where AR-RS 408 can receive AKs and serve as anauthenticator for mobile stations 416 and 418. In order to update theAKs of mobile stations 416 and 418, AR-RS 408 may issue a rangingmessage 1504 to target base station 1600 that indicates to base station1600 that AR-RS 408 is within or approaching the coverage area fortarget base station 1600. After AR-RS 408 undergoes 802.1Xauthentication 206 with gateway 1602, gateway 1602 transfers the AK forthe mobile relay station at AK Transfer 1606. AR-RS 408 may also undergoSA-TEK 3-way handshake 214 to obtain traffic keys for further datatransmission of, for example, tunnel packets or to relay mobile stationmessages.

AR-RS 408 transmits a re-authentication trigger message 1508 to mobilestations 416 and 418. Upon receipt of the re-authentication triggermessage 1508, the mobile stations 416 and 418 perform 802.1Xauthentication with gateway 1602 and AAA server 104. Gateway 1602calculate a new AK for each of the mobile stations 416 and 418 andtransfers all of the AKs for the mobile stations associated with AR-RS408 at AK Transfer 1608 to AR-RS 408. In one embodiment, AR-RS 408operates as an AR-RS and has the ability to authenticate mobile stationsdirectly. Gateway 1602 may transmit the AKs corresponding to mobilestations 416 and 418 in tunnel mode. Mobile stations 416 and 418 thenundergo SA-TEK 3-way handshake 214 with AR-RS 408. AR-RS 408 willprovide traffic keys for each of the mobile stations to AR-RS 408 usingSA-TEK 3-way transfer. Alternatively, AR-RS 408 may optionally avoidgenerating new traffic keys for mobile stations 416 and 418 if itreceives the traffic keys from another AR-RS or from target base station1602.

FIG. 17 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station, inwhich the base stations are connected to the same gateway. In FIG. 17,AR-RS 408 has moved or is about to move from the coverage area for basestation 1502 (FIG. 15) into the coverage area for target base station1702. Target base station 1702 is served by the same gateway 106 as thecurrent base station 1502. AR-RS 408 issues ranging message 1504 totarget base station 1702 that indicates to base station 1702 that AR-RS408 is within or approaching the coverage area for target base station1702. AR-RS 408 must authenticate with gateway 106 and performauthentication protocols such as SA-TEK 3-way handshake 214. After AR-RS408 is authenticated, gateway 106 transmits AKs for mobile stations 416and 418 to AR-RS 408 at AK Transfer 1706. When multiple AKs are beingsent from gateway 106 to AR-RS 408, gateway 106 may transmit the AKs bytunnel mode at AK Transfer 1706. AR-RS 408 transmits re-authenticationtrigger message 1508 to mobile stations 416 and 418. Upon receipt of there-authentication trigger message 1508, mobile stations 416 and 418perform SA-TEK 3-way handshake 214 with AR-RS 408 to update theirrespective AKs, and may do so with or without also updating theirrespective traffic keys. In one embodiment, the AKs are received atAR-RS 408 prior to the inter-base station handoff to avoid a disconnectof service to mobile stations 416 and 418.

FIG. 18 is a signaling diagram of an exemplary mobile relay stationhandoff between a current base station and a target base station, inwhich the base stations are connected to the same gateway. In FIG. 18,AR-RS 408 has moved or is about to move from the coverage area for basestation 1502 into the coverage area for target base station 1702. AR-RS408 issues ranging message 1504 to target base station 1702 thatindicates to base station 1702 that AR-RS 408 is within or approachingthe coverage area for target base station 1702. Upon receipt of rangingmessage 1504, target base station 1702 transmits AKs for each of themobile stations 416 and 418 to AR-RS 408. This is possible because basestation 1702 has access to AKs for mobile station 416 and 418 due totheir previous authentication with a base station 1502 within gateway106. When multiple AKs are being sent from target base station 1502 toAR-RS 408, target base station 1502 may transmit the AKs by tunnel modeat an AK Transfer 1802. AR-RS 408 transmits a re-authentication triggermessage 1508 to mobile stations 416 and 418. Upon receipt of there-authentication trigger message 1508, the mobile stations 416 and 418perform SA-TEK 3-way handshake 214 with AR-RS 408 to update theirrespective AKs, and may do so with or without also updating theirrespective traffic keys. In one embodiment, the AKs are received atAR-RS 408 prior to the inter-base station handoff to avoid a disconnectin service to mobile stations 416 and 418.

One of skill in the art will also appreciate that, in each of thescenarios illustrated above in connection with FIGS. 15-18, instead ofsending AKs to target base station 1502, gateway 106 may send differentsecurity material, such as, for example, a verification keycorresponding to AR-RS 408. Similarly, instead of sending AKs for mobilestations 416 and 418 to AR-RS 408, target base station 1502 may senddifferent security material, such as, for example, verification keyscorresponding to the mobile stations 416 and 418.

CONCLUSION

Systems and methods disclosed herein may be implemented in digitalelectronic circuitry, or in computer hardware, firmware, software, or incombinations of them. Apparatus embodying the invention can beimplemented in a computer program product tangibly embodied in amachine-readable storage device for execution by a programmableprocessor. Method steps consistent with the invention can be performedby a programmable processor executing a program of instructions toperform functions of the invention by operating on the basis of inputdata, and by generating output data. Embodiments consistent with theinvention may be implemented in one or several computer programs thatare executable in a programmable system, which includes at least oneprogrammable processor coupled to receive data from, and transmit datato, a storage system, at least one input device, and at least one outputdevice, respectively. Computer programs may be implemented in ahigh-level or object-oriented programming language, and/or in assemblyor machine code. The language or code can be a compiled or interpretedlanguage or code. Processors may include general and special purposemicroprocessors. A processor receives instructions and data frommemories. Storage devices suitable for tangibly embodying computerprogram instructions and data include all forms of non-volatile memory,including by way of example semiconductor memory devices, such as EPROM,EEPROM, and flash memory devices; magnetic disks such as internal harddisks and removable disks; magneto-optical disks; and CD-ROM disks. Anyof the foregoing can be supplemented by or incorporated in ASICs(application-specific integrated circuits).

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the system and method forestablishing security associations in wireless communications systems.For example, one of skill in the art will appreciate that rangingrequests and responses are a type of signaling message and that othersignaling messages may be used. In addition, one of skill in the artwill appreciate that traffic encryption keys are a type of traffic keyand that other traffic keys may be used, and that MACKs are a type ofverification key and that other verification keys may be used. One ofskill in the art will also appreciate that communication between basestations and relay stations can be wireless or wired. It is intendedthat the standard and examples be considered as exemplary only, with atrue scope of the disclosed embodiments being indicated by the followingclaims and their equivalents.

1. A method of providing secure communications between a base station, arelay station, and a mobile station in a communication network, themethod comprising: receiving, by the relay station, an unsolicitedsecurity key from the base station; receiving, by the relay station, asignaling message from the mobile station; and authenticating, by therelay station, the mobile station using the security key.
 2. The methodof claim 1, wherein the receiving of the signaling message includesreceiving a ranging request.
 3. The method of claim 1, further includingreceiving the security key as master key.
 4. The method of claim 3,further including receiving the master key as an authentication key(AK).
 5. The method of claim 1, further including receiving the securitykey as a verification key.
 6. The method of claim 5, wherein receivingthe security key as a verification key includes receiving the securitykey as a message authentication code key (MACK).
 7. The method of claim1, further including receiving the signaling message including a messageauthentication code (MAC) corresponding to the mobile station; whereinthe authenticating comprises verifying the MAC using the security key.8. The method of claim 1, further comprises performing, by the relaystation, at least one of a security association signaling protocol and atraffic encryption key (TEK) 3-way handshake with the mobile station. 9.The method of claim 8, wherein performing, by the relay station, atleast one of a security association signaling protocol and a TEK 3-wayhandshake with the mobile station comprises performing at least one of asecurity association-traffic encryption key (SA-TEK) 3-way handshake anda TEK 3-way handshake with the mobile station.
 10. The method of claim1, further comprising: generating, by the relay station, a traffic key;and transmitting, by the relay station, encrypted data to the mobilestation using the traffic key.
 11. The method of claim 1, furthercomprising moving, by the relay station, to a service area of adifferent base station.
 12. The method of claim 1, wherein communicationbetween the base station and the relay station is wireless.
 13. A methodof providing secure communications between a base station, a relaystation, and a mobile station in a communication network, the methodcomprising: receiving, by the relay station, a signaling message fromthe mobile station; transmitting, by the relay station, subsequent toreceiving the signaling message, a security key request to the basestation; receiving, by the relay station, a security key from the basestation in response to the previously sent security key request; andauthenticating, by the relay station, the mobile station using thereceived security key.
 14. The method of claim 13, wherein the receivingof the signaling message includes receiving a ranging request.
 15. Themethod of claim 13, further including receiving the security key as amaster key.
 16. The method of claim 15, further including receiving themaster key as an authentication key (AK).
 17. The method of claim 13,further comprising receiving the security key as a verification key. 18.The method of claim 17, wherein receiving the security key as averification key includes receiving the security key as a messageauthentication code key (MACK).
 19. The method of claim 13, furtherincluding receiving the signaling message including a messageauthentication code (MAC) corresponding to the mobile station; whereinthe authenticating comprises verifying the MAC using the security key.20. The method of claim 13, further comprises performing, by the relaystation, at least one of a security association signaling protocol and atraffic encryption key (TEK) 3-way handshake with the mobile station.21. The method of claim 20, wherein performing, by the relay station, atleast one of a security association signaling protocol and a TEK 3-wayhandshake with the mobile station comprises performing at least one of asecurity association-traffic encryption key (SA-TEK) 3-way handshake anda TEK 3-way handshake with the mobile station.
 22. The method of claim13, further comprising: generating, by the relay station, a traffic key;and transmitting, by the relay station, encrypted data to the mobilestation using the traffic key.
 23. The method of claim 13, furthercomprising moving, by the relay station, to a service area of adifferent base station.
 24. The method of claim 13, whereincommunication between the base station and the relay station iswireless.
 25. A method of providing secure communications between atarget base station, a mobile relay station, and at least one mobilestation in a communication network, the method comprising: transmitting,by the mobile relay station, a signaling message to the target basestation, the signaling message including a message authentication code(MAC) corresponding to the at least one mobile station; receiving, bythe mobile relay station, a responsive signaling message from the targetbase station; receiving, by the mobile relay station, at least onesecurity key corresponding to the at least one mobile station from thetarget base station; and authenticating, by the mobile relay station,the at least one mobile station using the corresponding security key.26. The method of claim 25, wherein the receiving at least one securitykey corresponding to the at least one mobile station includes receivingthe at least one security key in a secure tunnel mode.
 27. The method ofclaim 25, wherein the authenticating comprises performing IEEE 802.1Xauthentication.
 28. The method of claim 25, further comprisingperforming at least one of a security association signaling protocol anda traffic encryption key (TEK) 3-way handshake between the mobile relaystation and the target base station.
 29. The method of claim 28, whereinperforming, by the relay station, at least one of a security associationsignaling protocol and a TEK 3-way handshake with the mobile stationcomprises performing at least one of a security association-trafficencryption key (SA-TEK) 3-way handshake and a TEK 3-way handshake withthe mobile station.
 30. The method of claim 25, wherein the receiving atleast one security key comprises receiving the at least one security keyin tunnel mode.
 31. The method of claim 25, wherein the receiving atleast one security key comprises receiving an authentication key (AK).32. The method of claim 25, further including receiving the security keyas a verification key.
 33. The method of claim 32, wherein receiving thesecurity key as a verification key includes receiving the security keyas a message authentication code key (MACK).
 34. The method of claim 25,wherein communication between the target base station and the mobilerelay station is wireless.
 35. A relay station for providing securecommunications in a communication network, the relay station comprising:at least one memory to store data and instructions; and at least oneprocessor configured to access the memory and configured to, whenexecuting the instructions: authenticate, in response to a signalingmessage received from a mobile station, the mobile station using anunsolicited security key received from a base station.
 36. The relaystation of claim 35, wherein the signaling message is a ranging request.37. The relay station of claim 35, wherein the security key is a masterkey.
 38. The relay station of claim 37, wherein the master key is anauthentication key (AK).
 39. The relay station of claim 35, wherein thesecurity key is a verification key.
 40. The relay station of claim 39,wherein the verification key is a message authentication code key(MACK).
 41. The relay station of claim 35, wherein the signaling messageincludes a message authentication code (MAC) corresponding to the mobilestation and the authenticating comprises verifying the MAC using thesecurity key.
 42. The relay station of claim 35, wherein the processoris further configured to, when performing the instructions: perform atleast one of a security association signaling protocol and a trafficencryption key (TEK) 3-way handshake with the mobile station.
 43. Therelay station of claim 42, wherein the security association signalingprotocol is a security association-traffic encryption key (SA-TEK) 3-wayhandshake.
 44. The relay station of claim 35, wherein the processor isfurther configured to, when performing the instructions: generate atraffic key; and transmit encrypted data to the mobile station using thetraffic key.
 45. The relay station of claim 35, wherein the relaystation is a mobile relay station.
 46. The relay station of claim 35,wherein communication between the base station and the relay station iswireless.
 47. A relay station for providing secure communications in acommunication network, the relay station comprising: at least one memoryto store data and instructions; and at least one processor configured toaccess the memory and configured to, when executing the instructions:subsequent to receiving a signaling message from a mobile station,transmit a security key request to a base station; and authenticate themobile station using a security key received from the base station inresponse to the previously transmitted security key request.
 48. Therelay station of claim 47, wherein the signaling message is a rangingrequest.
 49. The relay station of claim 47, wherein the security key isa master key.
 50. The relay station of claim 47, wherein the master keyis an authentication key (AK).
 51. The relay station of claim 47,wherein the security key is a verification key.
 52. The relay station ofclaim 47, wherein the verification key is a message authentication codekey (MACK).
 53. The relay station of claim 47, wherein the signalingmessage includes a message authentication code (MAC) corresponding tothe mobile station and the authenticating comprises verifying the MACusing the security key.
 54. The relay station of claim 47, wherein theprocessor is further configured to, when performing the instructions:perform at least one of a security association signaling protocol and atraffic encryption key (TEK) 3-way handshake with the mobile station.55. The relay station of claim 54, wherein performing, by the relaystation, at least one of a security association signaling protocol and aTEK 3-way handshake with the mobile station comprises performing atleast one of a security association-traffic encryption key (SA-TEK)3-way handshake and a TEK 3-way handshake with the mobile station. 56.The relay station of claim 47, wherein the processor is furtherconfigured to, when performing the instructions: generate a traffic key;and cause transmission of encrypted data to the mobile station using thetraffic key.
 57. The relay station of claim 47, wherein the relaystation is a mobile relay station.
 58. The relay station of claim 47,wherein communication between the base station and the relay station iswireless.
 59. A base station for providing secure communications in acommunication network, the base station comprising: at least one memoryto store data and instructions; and at least one processor configured toaccess the memory and configured to, when executing the instructions:cause transmission of, in response to an indication that a mobilestation entered into a coverage area of a base station, an unsolicitedmaster key received from an authentication, authorization, andaccounting server to a relay station.
 60. The base station of claim 59,wherein the unsolicited master key is an authentication key (AK)
 61. Thebase station of claim 59, wherein communication between the base stationand the relay station is wireless.
 62. A base station for providingsecure communications in a communication network, the base stationcomprising: at least one memory to store data and instructions; and atleast one processor configured to access the memory and configured to,when executing the instructions: cause transmission of a security key toa relay station in response to a security key request received from arelay station.
 63. The base station of claim 62, wherein communicationbetween the base station and the relay station is wireless.
 64. A systemfor providing secure communications, the system comprising: a basestation configured to provide access to a communication network,authenticate a mobile station over the network, receive at least onesecurity key, and pre-distribute the at least one security key; and arelay station in communication with the base station for receiving thepre-distributed at least one security key unsolicited, and for providingsecure data transmissions to the authenticated mobile station using thesecurity key, wherein the security key comprises a master key.
 65. Thesystem of claim 64, wherein the master key is an authentication key(AK).
 66. The system of claim 64, wherein the verification key is amessage authentication code key (MACK).
 67. The system of claim 64,wherein communication between the base station and the relay station iswireless.
 68. A system for providing secure communications, the systemcomprising: a base station configured to provide access to acommunication network, authenticate a mobile station over the network,receive at least one security key, receive at least one security keyrequest, and transmit the at least one security key in response to thesecurity key request; and a relay station in communication with the basestation for transmitting the at least one security key request to thebase station, for receiving the at least one security key from the basestation in response to the security key request, and for providingsecure data transmissions to a mobile station using the security key,wherein the security key comprises at least one of an authentication key(AK) and a verification key.
 69. The system of claim 68, wherein theverification key is a message authentication code key (MACK).
 70. Thesystem of claim 68, wherein communication between the base station andthe relay station is wireless.
 71. A method of providing securecommunications between a base station, a relay station, and a mobilestation in a communication network, the method comprising: performingkey distribution upon receipt of a key request from the relay station todistribute a verification key corresponding to the mobile station to therelay station; and performing key verification, by the relay station, toidentify the mobile station.
 72. The method of claim 71, whereinperforming key distribution to distribute a verification key includesdistributing a message authentication code key (MACK).
 73. The method ofclaim 71, further comprising: performing key verification, by the mobilestation, to identify the relay station.
 74. The method of claim 71,wherein communication between the base station and the relay station iswireless.
 75. A method of providing secure communications between a basestation, a relay station, and a mobile station in a communicationnetwork, the method comprising: performing key pre-distribution todistribute an unsolicited verification key corresponding to the mobilestation to the relay station; and performing key verification, by therelay station, to identify the mobile station.
 76. The method of claim75, wherein performing key distribution to distribute a verification keyincludes distributing a message authentication code key (MACK).
 77. Themethod of claim 75, further comprising: performing key verification, bythe mobile station, to identify the relay station.
 78. The method ofclaim 75, wherein communication between the base station and the relaystation is wireless.
 79. A method of providing secure communicationsbetween a base station, a relay station, and a mobile station in acommunication network, the method comprising: performing keyverification, by the relay station, to identify the mobile station; andperforming key verification, by the mobile station, to identify therelay station.
 80. The method of claim 79, wherein communication betweenthe base station and the relay station is wireless.